Piezoelectric vibrating devices and methods for manufacturing same

ABSTRACT

An exemplary piezoelectric device includes a piezoelectric vibrating piece, on which excitation electrodes are formed, and a piezoelectric frame having a frame portion surrounding the piezoelectric vibrating piece. A plate (e.g., lid or base) is bonded to one surface of the frame portion. Fitting members are provided on both the frame and the plate. When the piezoelectric frame and plate are brought together for assembly, the fitting members fit together (e.g., interdigitate) to provide quick and error-free alignment. Then, the fitting members are bonded together by a bonding material.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Japan PatentApplication No. 2009-213926, filed on Sep. 16, 2009, in the Japan PatentOffice, the disclosure of which is incorporated herein by reference inits entirety.

FIELD

This disclosure relates to, inter alia, piezoelectric vibrating devicesand methods for manufacturing them, particularly in a manner suitablefor mass-production.

DESCRIPTION OF THE RELATED ART

Nowadays, crystal vibrating devices used in mobile communicationsdevices and/or OA equipment must increasingly be miniaturized, providedwith a thinner profile, and/or made to operate at a higher frequency soas to be correspondingly accommodated in electronic devices thatlikewise are increasingly miniaturized, provided with a thinner profile,and/or made to operate at a higher frequency. Also, for economicviability, devices satisfying these criteria must be mass-producible atincreasingly lower cost.

Certain methods for manufacturing piezoelectric vibrating devices aredisclosed in Japan Unexamined Patent Application No. 2008-182468. Eachdevice includes a “package” including a lid. Each lid is mounted on arespective guiding portion on a “package wafer” on which a plurality ofpackages has been formed, wherein each package accommodates a respectivepiezoelectric vibrating piece. During manufacture each lid and packageare fitted together by the guiding portion, and each package ishermetically sealed. Then, each package is cut from the package wafer,thereby producing multiple individual piezoelectric devices. The methoddisclosed in JP '468 can prevent misalignment of the package base andlid. However, in the method of JP '468ed in JP '468, multiple packagesare formed integrally on a single wafer, whereas the lids are formedindividually. As a result, each lid must be mounted individually on itsrespective package on the wafer, which imposes additional manufacturingsteps to produce the piezoelectric vibrating devices.

In view of the above, methods as disclosed herein increase productivityof piezoelectric vibrating devices while providing such devices thatexhibit high stability of vibrational frequency for long periods.

SUMMARY

A first aspect of the invention pertains to piezoelectric vibratingdevices. An exemplary device comprises a piezoelectric frame thatincludes a piezoelectric vibrating piece on which excitation electrodesare formed and a frame portion surrounding the piezoelectric vibratingpiece. The device also includes a plate (e.g., a base plate or lidplate) bonded to one surface of the frame portion of the piezoelectricframe. A respective fitting member is formed on the frame portion and onthe plate. The fitting members are configured to engage each other(e.g., interdigitate or fit one within the other) whenever thepiezoelectric frame and plate are aligned and brought together forassembly. In the device the respective fitting members are bondedtogether by a bonding material. The fitting members can includerespective metal films, in which event the bonding material can comprisea metal material. Alternatively, the bonding material can be a resinmaterial (e.g., an epoxy resin), in which event the metal films are notrequired in the fitting members. Desirably a corrosion-resistant film isformed on the exterior of the piezoelectric vibrating device. Thecorrosion-resistant film comprises an inorganic oxide film, a nitridefilm, or a nitric oxide film, or a combination thereof.

The plate can comprise glass, ceramic, or a piezoelectric material. Thepiezoelectric vibrating piece can be an AT-cut crystal vibrating pieceor a tuning-fork type crystal vibrating piece.

In a representative embodiment of a method for manufacturing the subjectpiezoelectric devices, a piezoelectric wafer is prepared that definesmultiple piezoelectric vibrating pieces and respective frame portionssurrounding each piezoelectric vibrating piece. Each piezoelectricvibrating piece comprises at least one excitation electrode, and eachframe portion defines first fitting members. Also prepared is a platewafer that defines multiple plates sized substantially similarly torespective frame portions on the piezoelectric wafer. Each plate definessecond fitting members configured to physically engage (e.g.,interdigitate with or fit one within the other) with respective firstfitting members whenever the plate wafer is aligned with and broughttogether with the piezoelectric wafer. A bonding material is placedbetween the first fitting members and the second fitting members. Thepiezoelectric wafer and the plate wafer are aligned and bonded themtogether using the placed bonding material, thereby forming a packagewafer.

By this method, a plurality of devices can be manufacturedsimultaneously on a single package wafer, thereby improvingmanufacturing efficiency.

After bonding, the bonded wafer can be cut along the outside peripheryof the frame portion. A slit can be formed that extends between thefirst fitting member and the second fitting member. Acorrosion-resistant film can be formed on the slit. Thecorrosion-resistant film desirably includes at least one of an inorganicoxide, a nitride, or a nitric oxide. At least one of the films is formedby chemical vapor deposition or sputtering.

The bonded wafer (“package wafer”) can be cut along the slit using anarrower blade than used to cut the slit.

Using the subject methods, multiple devices can be formed simultaneouslyon a single package wafer while improving the stability and durabilityof the piezoelectric devices thus produced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view of the inner surface of a lid for use in thepackage of a first embodiment of a crystal vibrating device.

FIG. 1B is a plan view of a crystal frame of the first embodiment, thecrystal frame including a tuning-fork type crystal vibrating piece.

FIG. 1C is a plan view of the inner surface of a base for use in thepackage of a first embodiment of a crystal vibrating device.

FIG. 1D is an elevational section along the line A-A in FIGS. 1A-1C.

FIG. 2 is a plan view of a package wafer comprising multiple crystalvibrating devices, as viewed from the lid side, according to the firstembodiment.

FIG. 3 is an enlarged elevational section along the line B-B of FIG. 2,showing a portion of the package wafer before actually bonding the threeconstituent wafers together.

FIG. 4 is a plan view of a package wafer according to a secondembodiment, as viewed from the lid side.

FIG. 5 is an enlarged elevational section along the line C-C of FIG. 4,showing a portion of the package wafer before actually bonding the threeconstituent wafers together.

FIG. 6A is an enlarged elevational section along the line D-D of FIG. 4.

FIG. 6B is the same as FIG. 6A but after a cut has been made between twoadjacent crystal vibrating devices.

FIG. 6C is the same as FIG. 6B but after a corrosion-resistant film hasbeen formed.

FIG. 6D is the same as FIG. 6C but after a cut has been made thatcompletely separates the devices from each other.

DETAILED DESCRIPTION

The invention is described below in the context of representativeembodiments that are not intended to be limiting in any way.

First Embodiment of a Crystal Vibrating Device

FIG. 1A is a plan view of the inner surface of a lid 10 of thisembodiment of a crystal vibrating device 100. FIG. 1B is a plan view ofthe crystal frame 20 of this embodiment, wherein the crystal frame 20comprises a tuning-fork type crystal vibrating piece 30. FIG. 1C is aplan view of the inner surface of a base 40 of this embodiment. FIG. 1Dis an elevational section along the line A-A in FIGS. 1A-1C, showing thecrystal vibrating device 100. The crystal vibrating device 100 comprisesa package including the crystal frame 20 sandwiched between the lid 10and the base 40.

The lid 10 and base 40 are each made of glass, ceramic, or crystal(quartz crystal) material. The crystal frame 20 includes the tuning-forktype crystal vibrating piece 30, which has an outline profile formed byetching.

As shown in FIG. 1A, the lid 10 has a concavity 17 that faces thecrystal frame 20. Around the periphery of the lid 10, facing the crystalframe 20, is a fitting concavity 73. The fitting concavity 73 includes ametal film 15 formed herein.

As shown in FIG. 1B, the crystal frame 20 comprises a tuning-fork typecrystal vibrating piece 30, an outer frame 29, and a pair of supportingarms 26. These components are formed integrally, with the samethickness, on the crystal wafer 20W (see FIG. 2). The tuning-fork typecrystal vibrating piece 30 comprises a pair of vibrating arms 21 and abase portion 23. Around the periphery of the outer frame 29 on thesurface shown in FIG. 1B is a fitting convexity 72. Similarly, aroundthe periphery of the outer frame 29 on the opposing surface is a fittingconcavity 73. Thus, both major surfaces of the crystal frame 20 haverespective fitting concavities. Each fitting concavity 72, 73 has arespective metal film 25 formed therein.

A first base electrode 31 and a second base electrode 32 are formed onthe outer frame 29, the base 23, and the supporting arms 26 of thecrystal frame 20. The vibrating arms 21 have a respective firstexcitation electrode 33 (on one vibrating arm) and a respective secondexcitation electrode 34 (on the other vibrating arm). On each vibratingarm 221, the respective excitation electrodes are provided on the upper,lower, and side surfaces thereof. The first excitation electrode 33 isconnected to a first base electrode 31, and the second excitationelectrode 34 is connected to a second base electrode 32. The tuning-forktype crystal vibrating piece 30 is very small, and oscillates at 32.768kHz.

Each of the first base electrode 31, second base electrode 32, firstexcitation electrode 33, and second excitation electrode 34 comprisesrespective metal layers. Example metal layers are 400-2000 Ångstroms ofgold (Au) layered on 150-700 Ångstroms of chromium (Cr).

The supporting arms 26 extend parallel to the vibrating arms 21 (in theY-direction) from one end of the base 23, and connect to the outer frame29. The supporting arms 26 reduce leakage of oscillations from thevibrating arms 21, oscillating inside of the package, to the exterior ofthe crystal vibrating device 100. The supporting arms 26 protect thedevice from adverse influences such as changes in external temperatureand/or physical impacts from dropping the package.

As shown in FIG. 1C, the base 40 defines a concavity 47 that faces thecrystal frame 20 in the package. The concavity 47, a first through-hole41, and a second through-hole 43 are all formed concurrently by etching.The base 40 also includes step portions 49 used for connectingelectrodes, specifically a first connecting electrode 42 and a secondconnecting electrode 44, formed thereon. On the under-surface of thebase 40 are a first external electrode EX1 and a second externalelectrode EX2, both of which are metalized. Just inboard of theperiphery of the base 40, facing the crystal frame 20, is a fittingconvexity 72 that includes a metal film 45 formed therein.

The first and second through-holes 41, 43 each include an interior metalfilm. Each metal film is formed, simultaneously with formation of thefirst and second connecting electrodes 42, 44, by photolithography. Thefirst connecting electrode 42 connects to the first external electrodeEX1 on the under-surface of the base 40 via the first through-hole 41.The second connecting electrode 44 connects to the second externalelectrode EX2 on the under-surface of the base 40 via the secondthrough-hole 43.

The first base electrode 31 and second base electrode 32, formed on theunder-surface of the outer frame 29, connect respectively to the firstconnecting electrode 42 and second connecting electrode 44 formed on theupper surface of the base 40. I.e., the first base electrode 31 iselectrically connected to the first external electrode EX1, and thesecond base electrode 32 is electrically connected to the secondexternal electrode EX2.

The metal film 25 formed on the crystal frame 20 comprises a layer ofgold (Au; 400 to 1500 Å thick) that may be formed on a layer of chromium(Cr; 150 to 700 Å thick). Specifically, whenever the lid and base aremade of a crystal material, the metal films 15, 45 each include a goldlayer formed on a chromium layer. Whenever the lid and base are made ofglass or ceramic, the metal films 15, 45 each include only the goldlayer.

As shown in FIG. 1D, a crystal vibrating device 100 is formed bylayering together the lid 10 of FIG. 1A, the crystal frame 20 of FIG.1B, and the base 40 of FIG. 1C. These parts, exclusive of thetuning-fork type crystal vibrating piece 30, are called the “package”80. In FIG. 1D, each of these parts is illustrated separately forclarity of depiction. The first and second through-holes 41, 43 of thepackage 80 are sealed by a sealing material 70.

Further with respect to FIG. 1D, fitting steps are formed on the bondingfaces of the lid 10, base 40, and crystal frame 20. More specifically,the fitting concavity 73 of the lid 10 fits into the fitting convexity72 of the crystal frame 20, and the fitting convexity 72 of the base 40fits into the fitting concavity 73 of the crystal frame 20.

In FIG. 1D the lid 10, base 40, and crystal frame 20 are not yet bondedtogether, but the figure indicates how these parts are aligned with eachother for bonding. During actual manufacture, a single crystal wafer 20Won which hundreds or thousands of crystal frames 20 are formed (see FIG.2), one lid wafer 10W on which hundreds or thousands of lids 20 areformed (see FIG. 3), and a base wafer 40W on which hundreds or thousandsof bases 40 are formed (see FIG. 3) are aligned, layered (with thecrystal wafer being sandwiched between the base and lid wafers), andbonded together to form hundreds or thousands of crystal vibratingdevices 100 simultaneously. The three-layer sandwich thus formed iscalled a package wafer 80W.

FIG. 2 is a top plan view of a package wafer 80W, as viewed from the lidwafer side. The lid wafer 10W is depicted as if it were transparent, andthe figure mainly shows the tuning-fork type crystal vibrating pieces 30formed on the crystal wafer 20W. For comprehension, an areacorresponding to the section of one crystal vibrating device 100 isdenoted with a virtual line (two-dotted chain line) on the package wafer80W. Also, voids 22 are depicted as meshed zones to distinguish thetuning-fork type vibrating piece 30 and the outer frame 29.

Further with respect to FIG. 2, cutting grooves 60 are formed on the lidwafer 10W. Cutting grooves 60 are also formed on the base wafer 40W (seeFIG. 3) aligned (in the X-Y plane) with the cutting grooves on the lidwafer 10W (X-Y plane). The package wafer 80W is affixed to a dicingfilm, not shown, and cut using a dicing saw. The cutting grooves 60 areused for preventing formation of cracks on the crystal vibrating device100 whenever the lid wafer 10W and the base wafer 40W are being cut bythe dicing saw. During cutting the dicing saw moves linearly between thewalls of the cutting grooves 60 of the lid wafer 10W and the base wafer40W. The depth of each cutting groove 60 is in the range of 20 to 40 μm.

Continuing further with FIG. 2, the metal film 15 formed on the lidwafer 10W, the metal film 25 formed on the crystal wafer 20W, and themetal film 45 formed on the base wafer 40W are situated so as to becomelayered with each other in the X-Y plane. Thus, the fitting concavity 73of the lid 10 fits within the fitting convexity 72 of the crystal frame20. The metal films 15, 25, and 45 are positioned so that they do notextend into the cutting grooves 60. This avoids the cutting saw fromcutting into the metal forms, which prevents formation of metal chipsthat could attach to the blade of dicing saw.

FIG. 3 is an enlarged elevational section, along the line B-B, of aportion of the package wafer 80W. For comprehension, an areacorresponding to the size of one crystal vibrating device 100 isillustrated within a virtual line (two-dotted line) on the package wafer80W. The package wafer 80W comprises a lid wafer 10W on which lids 10are formed, a crystal wafer 20W on which crystal frames 20 are formed,and a base wafer 40W on which bases 40 are formed. FIG. 3 shows theseportions of the package wafer 80W aligned with each other but not yetbonded together. In FIG. 3 the lid wafer 10W is situated below and thebase wafer 40W is situated above so that they sandwich the crystal wafer20W. On the lid wafer 10W and the base wafer 40W are respective cuttinggrooves 60 that are positioned according to the size of the crystalvibrating devices 100 formed between them.

On the inner surface of the lid wafer 10W a concavity 17 is formed bywet-etching. Also formed at the same time by wet-etching is the fittingconcavity 73 on the lid wafer 10W, facing the crystal wafer 20W. On theouter (upper) surface of the lid wafer 10W, the cutting grooves 60 areformed. On the inner surface of the base wafer 40W, a concavity 47 andfitting convexity 72 are formed by wet-etching. On the outer surface(under-surface) of the base wafer 40W are formed the cutting grooves 60.

On the surface of the crystal wafer 20W facing the lid wafer 10W, thefitting convexity 72 is formed by wet-etching. On the surface of thecrystal wafer 20W facing the base wafer 40W, the fitting concavity 73 isformed by wet-etching. The fitting concavity 73 formed on the lid wafer10W fits with the fitting convexity 72 of the crystal wafer 20W.Similarly, the fitting convexity 72 formed on the base wafer 40W fitswith the fitting concavity 73 of the crystal wafer 20W.

As shown in FIG. 3, the fitting concavity 73 of the lid wafer 10Wincludes the metal film 15. Similarly, the fitting convexity 72 and thefitting concavity 73 of the crystal wafer 20W include the metal film 25,and the fitting convexity 72 of the base wafer 40W includes the metalfilm 45.

A eutectic metal ball 75 can be placed in the fitting concavity 73 tomaintain a temporary space between the metal layers 25, 45. Afterinserting the fitting convexity 72 into the fitting concavity 73, as theeutectic metal ball 75 melts, the molten eutectic metal flows along themetal films 15, 25, 45. I.e., the molten eutectic metal wets thesurfaces of the metal film 15, 25, 45 by capillary action. When themolten eutectic metal cools, it hardens, resulting in bonding the metalfilms 15, 25 together and the metal films 25, 45 together. Thus, thepackage of the crystal vibrating device 100 of this embodiment is formedby interaction of the metal films 15, 25, 45.

The eutectic metal ball 75 desirably comprises a gold-silicon alloy(Au_(3.15)Si, wherein the percent w/w of Si is 3.15), a gold-germaniumalloy (Au₁₂Ge), or a gold-tin alloy (Au₂₀Sn). The melting temperature ofthe gold-silicon alloy is 363° C., of the gold-germanium alloy is 356°C., and of the gold-tin alloy is 280° C.

The first through-hole 41 and second through-hole 43 are sealed using asealing material 70. The sealing material 70 can be a eutectic, similarto the bonding material discussed above, namely a gold-silicone alloy, agold-germanium alloy, or a gold-tin alloy. If the same eutectic is usedfor both sealing and bonding, both can be done simultaneously. Forexample, sealing of the through-holes and bonding together of respectivewafers can be done at the same temperature by placing the packaged wafer80W in a reflow furnace under a preselected vacuum or filled with adesired inert gas.

Alternatively, the sealing material and bonding material can bedifferent. For example, a eutectic metal having a high meltingtemperature can be used first (e.g., for bonding), followed by use of aeutectic metal having a lower melting temperature (e.g., for sealing),since use of the second eutectic will not result in melting of the firsteutectic.

Note that the cut regions between adjacent crystal vibrating devices 100(indicated in FIG. 3 by two-dotted chain lines) do not extend into themetal films 15, 25, 45. Thus, the regions occupied by melted eutectic donot extend into cut regions, either. Hence, whenever the crystalvibrating devices 100 are being cut into individual devices by a dicingsaw, the dicing saw does not cut the metal films. As a result, thedicing saw blade does not form chips or cracks on the package wafer 80Wthat otherwise would be caused by friction of the dicing saw withmetals.

Since the lid wafer 10W and the base wafer 40W are provided with cuttinggrooves 60, the cutting load otherwise imposed on the dicing saw isreduced, which improves work efficiency. During dicing the lid wafer 10Wand base wafer 40W are affixed to a dicing tape and then diced. Thecutting grooves prevent metal chips from interfering with the lid wafer10W and base wafer 40W.

Second Embodiment of a Crystal Vibrating Device

FIG. 4 is a top plan view of a package wafer 85W as viewed from the lidwafer 10WA. The lid wafer 10WA is shown as if it were transparent,revealing the underlying tuning-fork type crystal vibrating pieces 30formed on the crystal wafer 20WA. For comprehension, the areacorresponding to the profile of one crystal vibrating device 110 isdelineated with a virtual line (two-dotted chain line) on the packagedwafer 85W. Also the voids 22 are denoted as meshed regions todistinguish them from the tuning-fork type vibrating piece 30 and theouter frame 29.

As shown in FIG. 4, cutting grooves 60 are provided on the lid wafer10WA and on the base wafer 40WA at corresponding locations in the X-Yplane (see FIG. 5) as on the lid wafer 10WA. Fitting concavities 68 andfitting convexities 69 are denoted by solid lines in a regioncorresponding to the profile of one crystal vibrating device 110.

FIG. 5 is an enlarged elevational section, along the line C-C in FIG. 4,of a package wafer 85W including a crystal vibrating device 110. In FIG.5 the wafers are aligned but not yet brought into contact with eachother. In this embodiment a resin (e.g., epoxy resin) is used as abonding material for forming the package of the crystal vibrating device110. For comprehension of FIG. 5, areas corresponding to the size ofrespective crystal vibrating devices 110 are delineated with virtuallines (two-dotted chain lines) on the package wafer 85W.

As shown in FIG. 5, the package wafer 85W comprises a lid wafer 10WA, onwhich individual lids 10A are formed, a crystal wafer 20WA, on whichindividual crystal frames 20A are formed, and a base wafer 40WA on whichbases 40A are formed. For comprehension, FIG. 5 depicts shows thepackage wafer 85WA in which the constituent wafer are aligned but notyet bonded together. In FIG. 5, the lid wafer 10WA is at the bottom andthe base wafer 40WA at the top, with the crystal wafer 30WA beingsandwiched therebetween. On the lid wafer 10WA and base wafer 40WA arecutting grooves 60 placed according to the sizes of the crystalvibrating devices.

A concavity 17 is formed by wet-etching the inner surface of the lidwafer 10WA. At the same time, the fitting concavity 68 facing thecrystal wafer 20WA can also be formed on the lid wafer 10WA bywet-etching. On the opposite surface of the lid wafer 10WA (i.e., on theouter surface) are the cutting grooves 60. Also on the base wafer 40WA,a concavity 47 and the fitting convexity 69 are formed by wet etching.The cutting grooves 60 are spaced apart according to the size of thecrystal vibrating device 110, and are formed by wet-etching the basewafer 40WA as well.

On the surface of the crystal wafer 20WA facing the lid wafer 10WA,fitting convexities 69 are formed by wet-etching. Similarly, on theopposite surface, fitting concavities 68 are formed by wet-etching. Thefitting concavity 68 on the lid wafer 10WA receives the fittingconvexity 69 formed on the crystal wafer 20WA. Similarly, the fittingconvexity 69 formed on the base wafer 40WA fits into the fittingconcavity 68 formed on the crystal wafer 20WA. Metal films are notformed on the fitting convexities 69 or fitting concavities 68 becausebonding the wafers of the crystal vibrating devices 110 together issimply performed using a resin (e.g., epoxy resin). Other resins thatcould be used include silicone resins and polyimide resins, orcombinations thereof.

Method for Manufacturing Crystal Vibrating Device of Second Embodiment

FIGS. 6A, 6B, 6C, and 6D are enlarged elevational sections along theline D-D in FIG. 4. These figures are of a package wafer 85W includingthe crystal vibrating device 110. FIGS. 6A-6D also show respectivemanufacturing steps for making the crystal vibrating device 110. Areascorresponding to the size of the crystal vibrating device 110 aredelineated with virtual lines (two-dotted chain lines) on the packagewafer 85W.

In FIG. 6A the lid wafer 10WA is shown on which the lids 10A are formed,the crystal wafer 20WA is shown on which crystal frames 20A havingrespective tuning-fork type crystal vibrating pieces 30 are formed, andthe base wafer 40WA is shown on which the bases 40A are formed. Thewafers are shown as respective layers that are aligned but not yetbonded together. The fitting concavities 68 of the wafers receiverespective fitting convexities 69 and are bonded thereto. An adhesive isapplied on the fitting concavities 68 so as not to be separated,resulting in layering of the three wafers.

On the lid wafer 10WA and base wafer 40WA are formed respective cuttinggrooves 60. The cutting grooves 60 are not required, but when presentprevent cracking of the package wafer 85W during dicing.

The concavity 17 and the cutting grooves 60 on the lid 10A are formed byetching prior to bonding of the wafers together. Similarly, theconcavity 47 and the cutting grooves 60 can be formed simultaneously bywet-etching. Also formable by wet-etching are the first connectingelectrode 42 and second connecting electrode 44.

To bond together the mating surfaces of the lid wafer 10WA, crystalwafer 20WA, and base wafer 40WA, the wafers are first aligned, thenbonded. Bonding is performed by application of epoxy resin on thebonding surfaces and bringing the wafers together to form a sandwich.During bonding the layered wafers desirably are pressed (in an airenvironment) to achieve strong bonds by the epoxy, thereby forming apackage wafer 85W. During bonding, the first and second base electrodes31, 32 (FIG. 5) and the first and second connecting electrodes 42, 44are also bonded together strongly.

A unit of sealing material 70 is placed on each of the first and secondthrough-holes 41, 43 of the package wafer 85W. The package wafer 85W isplaced in a vacuum reflow furnace (not shown) providing a vacuum orinert-gas environment for sealing. The sealing material 70 can begold-germanium alloy (Au₁₂Ge), which melts at 356° C.

FIG. 6B is an elevational section showing formation of a slit 87. Thepackage wafer 85W is cut, using a dicing saw, along the cutting grooves,which forms the slit 87. The depth of the slit 87 extends through theregion in which the fitting convexity 69 and fitting concavity 68 havebeen layered and bonded together. Considering the crystal vibratingdevice 110 not as a wafer but as an individual device, the slit 87 canbe cut to the lower surface of the package wafer 85W, thereby releasingthe crystal vibrating device 110.

FIG. 6C is an elevational section depicting formation of acorrosion-resistant film 90. The corrosion-resistant film 90 is formedon the package wafer 85W on the upper surface of the lids and in regionsin which the slits 87 have been formed. The corrosion-resistant film 90is formed by chemical vapor deposition (CVD) and physical vapordeposition (PVD) on the side surfaces and top surface of the packagewafer 85W. The corrosion-resistant film 90 desirably is applied thicklyto the side surfaces of the fitting convexity 69 and fitting concavity68.

The corrosion-resistant film 90 can be formed of at least one of aninorganic oxide film, a nitride film, or a nitric oxide film. The filmcan be formed as a double-layer of inorganic oxide and nitride,respectively. The inorganic oxide film can be, for example, a silica(SiO₂) film, a titanium oxide (TiO₂) film, or an aluminum oxide (Al₂O₃)film. The nitride film can be a silicon nitride (Si₃N₄) film or analuminum nitride (AlN) film. The nitride oxide film can be a siliconeoxide nitride (Si₂ON₂) film.

The fitting convexity 69 and fitting concavity 68 of the crystalvibrating device 110 are bonded together using an adhesive, such as aresin (e.g., epoxy resin). Adhesives such as these tend to exhibitadhesion degradation over time. This results in difficulty of keepingthe interior of the crystal vibrating device 110 in a vacuum state orfilled with a desired concentration of inert gas for long periods oftime. Use of the corrosion-resistant film 90 overcomes this problem sothat the inside of the crystal vibrating device 110 can be kept at avacuum or at a desired concentration of inert gas for long periods.

Chemical vapor deposition (CVD) is a method by which a thin film isdeposited through deposition, reaction, and desorption on a surface of asubstrate after applying energy, such as plasma, to components of thinfilms provided as gases to form intermediate products of the gas.Physical vapor deposition (PVD) is a method by which a thin film can bedeposited on a substrate by evaporating a material to be deposited withenergy, such as heat or plasma. Typical PVD methods include vacuumdeposition and sputtering.

FIG. 6D is an elevational section of crystal vibrating devices 110 thathave been cut into individual devices. A cut region 96 is formed by adicing saw that is narrower than the slit 87 along the length of theslit 87. Thus, the package wafer 85W is cut into many individual crystalvibrating devices 110 by dicing.

FIGS. 6A and 6B show that the slit 87 is formed on the package wafer 85Wafter the first and second through-holes 41, 43 have been sealed by thesealing material 70. But, this is not intended to be limiting.Alternatively, for example, the package wafer 85W can be sealed in avacuum or inert-gas atmosphere after the slit 87 and thecorrosion-resistant film 90 have been formed.

Preferred embodiments of the present invention, including the crystalvibrating devices 100 and 110, are described above. According to theseembodiments, the air-tightness of the devices is improved by forming thepackage with fitting members on the lid, the piezoelectric frame, andthe base. Also, the embodiments are described in the context oftuning-fork type crystal resonator having vibrating arms on whichgrooves are not formed. However, it will be understood that theresonator alternatively can have vibrating arms with grooves or can beconfigured as crystal resonator using AT-cut crystal units exhibiting“thickness shear vibration.” Furthermore, any of various combinations ofshapes of bonding surfaces, fitting members, and bonding materials canbe used.

1. A piezoelectric vibrating device, comprising: a piezoelectric framecomprising a piezoelectric vibrating piece, on which excitationelectrodes are formed, and a frame portion surrounding the piezoelectricvibrating piece, the frame portion including first fitting members; anda plate bonded to one surface of the frame portion, the plate includingsecond fitting members; wherein the first and second fitting members arephysically engaged with each other and are bonded together using abonding material.
 2. The piezoelectric vibrating device of claim 1,wherein: the bonding material comprises at least one metal; the firstand second fitting members each include a metal film; and the first andsecond fitting members are bonded together by the bonding materialadhering to the metal films.
 3. The piezoelectric vibrating device ofclaim 2, wherein the plate comprises at least one of a glass, a ceramic,or a piezoelectric material.
 4. The piezoelectric vibrating device ofclaim 2, wherein the piezoelectric vibrating piece comprises an AT-cutcrystal vibrating piece or a tuning-fork type crystal vibrating piece.5. The piezoelectric vibrating device of claim 1, wherein the bondingmaterial comprises a resin.
 6. The piezoelectric vibrating device ofclaim 5, wherein the plate comprises at least one of a glass, ceramic,or a piezoelectric material.
 7. The piezoelectric vibrating device ofclaim 5, wherein the piezoelectric vibrating piece comprises an AT-cutcrystal vibrating piece or a tuning-fork type crystal vibrating piece.8. The piezoelectric vibrating device of claim 5, further comprising acorrosion-resistant film formed on an exterior surface of thebonded-together piezoelectric vibrating device.
 9. The piezoelectricvibrating device of claim 8, wherein the plate comprises at least one ofa glass, a ceramic, or a piezoelectric material.
 10. The piezoelectricvibrating device of claim 8, wherein the piezoelectric vibrating piececomprise an AT-cut crystal vibrating piece or a tuning-fork type crystalvibrating piece.
 11. The piezoelectric vibrating device of claim 8,wherein the corrosion-resistant film comprises at least one of aninorganic oxide, a nitride, or a nitric oxide.
 12. The piezoelectricvibrating device of claim 11, wherein the plate comprises at least oneof a glass, a ceramic, or a piezoelectric material.
 13. Thepiezoelectric vibrating device of claim 11, wherein the piezoelectricvibrating piece comprises an AT-cut crystal vibrating piece or atuning-fork type crystal vibrating piece.
 14. The piezoelectricvibrating device of claim 1, wherein the plate comprises at least one ofa glass, a ceramic, or a piezoelectric material.
 15. The piezoelectricvibrating device of claim 1, wherein the piezoelectric vibrating piececomprises an AT-cut crystal vibrating piece or a tuning-fork typecrystal vibrating piece.